Tech Tips Archive

MY FEET ARE CURLING UP!!!
January 2001
by Rod Carr

TriSpi mylar materials are manufactured in large rolls and then rewound onto smaller diameter tubing for shipment to manufacturers like model yacht sailmakers who turn the material into products. Being tightly wound can induce a certain amount of "set" into the material. This usually appears as a noticeable curl in the foot of sails which are built with some foot round (extra cloth outside of the straight line between the tack and the clew).

Such curling is minimized if the sails are rolled on their shipping tube in the opposite way that the material came from the manufacturer, but some residual curl may still be exhibited by the new sails.

Opposite rolling can only reduce the curl so much, and overdoing opposite rolling may induce damage to the clew and tack reinforcing patches.

Over time, the best approach seems to be mounting the sails on the rig and storing the rig in a vertical position with no tensions on halyards, downhauls, vangs, or outhauls. While a small, residual amount of curl may be observed in the feet of sails that are a couple months old, sails that are regularly used will quickly lose the curl. Small amounts of curl are not damaging to sail performance. Low speed winds quickly blow shape into the feet of the sails. Generally, the feet of the sails are working in turbulent air that is disturbed by its passage over the gunwale of the heeled hull.

Bottom line - - - focus on developing good sail camber and appropriate twist in the upper half of jib and main where the wind is moving fastest and capable of developing the greatest power. Once you can tune those parts of the sail well, turn your attention to making the jib and main work efficiently together on the beats by setting appropriate jib twist, and on the reaches by adjustment of the speed at which jib and main sheets let the sails out. If all these parts are working correctly, then take a peek at your feet, but don't forget to look up the course and see where the new wind is going to be coming from.